Garmin navigators will provide vertical guidance on almost every approach in the database. On LNAV approaches it will give you LNAV+V where the the +V refers to a pseudo glide path that is a mathematically derived 3 deg slope. This is very handy but care must be taken because it will not account for any mandatory crossing altitudes.
One gotcha with GARMIN systems is that the system switches from terminal mode to approach mode (ie LPV, LNAV/VNAV or LNAV) when the active leg is the leg to the FAF. If there is a fix between the IAF and the FAF it will not sequence to approach mode until after that waypoint which means there will be no glide path until after you pass the waypoint at which point you will be above the glide path.
The work around is to activate vectors to final after you pass the IAF which will cause the FAF to be the active to waypoint.